Invalid impressions are the impressions bought in real time by the DSP, but invalidated after, because they were not under the targeting or because they were invalid traffic or fraud. The Invalid Impressions plus Billable Impressions should make the total number of impressions.
Some DSP´s show the number of billable impressions. In DBM, for example, "the number of impressions that reached the intended or guaranteed audience. In a campaign with an audience guarantee, impressions that don't reach the agreed upon audience (as defined by Nielsen, comScore, vCE, or other
Impressions are the number of times an ad was displayed. Impressions refer to the number of times an ad (or group of ads) was displayed on a webpage, in an app, or in any other medium like video. When a user loads a page and sees 3 ad slots in
